effect of speakers in the corner

Well the placement is mainly goingto reinforce the lower frequencies.
Depending on your preferences, that can be Ok or not.
If you want to reduce the bass then yeah you need something to dampen the bass waves.
One cheap classic is piles of newspapers in the corners. (big piles, as tal las speaker) so if your foam is useful down in the lower frequencies, then it may help. If it is not, then the foam there is really wasted.

Toe in of the speakers may help considerably in lowering some bass peaks.

YES- You will be reinforcing your low freqs, with corner placement. These may help, if the effect is less than pleasing: (http://www.ebay.com/itm/Dark-Charcoal-Acoustic-Foam-Base-Absorbers-Traps-8pk-/260929001000?pt=LH_DefaultDomain_0&hash=item3cc0949628) A low cost, effective alternative to Auralex LENRDs.

Take a look at my secondary system. The speakers are close to the corners of a 10x14 room. I have Michael Green Room Tunes panels behind the speakers. They work great.

Note, the speakers I use have controlled directivity of the tweeter. A speaker with wider dispersion may not function as well close to a side wall.

Digital equalization is the way to go.

If you use a Mac, install Audio Hijack Pro, get an SPL meter, play 1/3 decade tones and fiddle with the 31-band graphic equalizer.

Speakers in the corner are often seen as a curse, but with access to an equalizer that turns into quite the blessing. You lucky dog, you might even be able to get a pair of Klipschorns. :)